THE HUMAN DIGESTIVE SYSTEMGRADE 8

SIR AARON RAFAEL RANOIS F. SAN JOSE

QUESTION

WHAT HAPPENS TO THE FOOD

ONCE DIGESTED?

QUESTION

HOW LONG DOES IT TAKE

TO DIGEST FOOD?

THREE MAIN FUNCTIONS

1. Ingestion of food2. Breakdown of food for cell

absorption3. Eliminating undigested

materials

DIGESTIVE SYSTEM

It is composed of different organs

cooperating for food digestion.

TYPES OF DIGESTIVE ORGANS

1. Accessory organs – assist in food digestion. (salivary glands, liver, gallbladder, pancreas)

2. Alimentary canal – contains organs where food passes through (mouth, pharynx, esophagus, stomach, small and large intestines, rectum, anus)

QUESTION

WHERE DOES DIGESTION

BEGIN?

A. THE ORAL CAVITY

Ingestion is the process from which the body take in the food through the mouth for digestion,

absorption and elimination.

A. THE ORAL CAVITY

The mouth or oral cavity is the first portion of the digestive tract or

alimentary canal.

TYPES OF DIGESTION

1. Chemical – involves the action of enzymes and other chemical substances in the body

2. Mechanical – involves the cutting, crushing or grinding of food using the teeth (mastication)

EXTERNAL TOOTH DIVISION

1. Crown2. Neck3. Root

INTERNAL TOOTH DIVISION

1. Enamel2. Dentin3. Pulp4. Cementum

FOUR TYPES OF HUMAN TEETH

1. Incisors (8 in adult)2. Cuspids (Canines)3. Bicuspids (Premolars) (8 in adult)4. Molars (12 in adult)

Third molars (wisdom)

FOUR TYPES OF HUMAN TEETH

WISDOM TEETH

THE PROCESS

Initial chemical digestion depends on an accessory organ – the salivary gland. Chemical digestion involves

enzymatic action, which is accomplished through the saliva.

SALIVARY GLANDS

1. Parotid gland – lies in front of ear; empties saliva near the second upper molar

2. Sublingual gland – lies under the floor of the mouth; empties saliva by numerous sublingual ducts

3. Submandibular gland – lies deep in the mouth; empties saliva on either side of the lingual frenulum (small fold under the tongue)

SALIVARY GLANDS

B. PHARYNX AND ESOPHAGUS

The bolus is the end product of the food that

has been chewed, partially digested, and

lubricated by the saliva.

QUESTION

HOW COME THE FOOD ENTER THE ESOPHAGUS AND DOES NOT GO THE

OTHER WAY? (RESPIRATORY TRACT)

B. PHARYNX AND ESOPHAGUS

A flap called epiglottis closes the air openings

when food is swallowed. It

prevents the bolus from entering the

trachea and ensures food enters the

esophagus.

C. THE STOMACH

The bolus passes through the stomach after leaving the esophagus. The

stomach is a highly muscularized J-shaped sac that stores food and

continues the digestion.

C. THE STOMACH

The environment is highly acidic.1. Chief cells – release pepsinogen (form

pepsin once in contact with acid)2. Goblet cells – produces mucus that

lines up the cells

C. THE STOMACH

Bolus

Chyme

C. THE STOMACH

Sphincters – prevent the stomach from leaking out gastric juicesCardiac sphincter – near esophagusPyloric sphincter – near s. intestine

D. THE SMALL INTESTINE

The longest part of digestive

tract.1. Duodenum2. Jejunum3. Ileum

D. THE SMALL INTESTINE

The completion of chemical digestion depends on three accessory organs –

pancreas, liver and gallbladder.END OF FOOD

DIGESTION!

C. THE SMALL INTESTINE

Enzyme Digestive organ Function

Salivary amylase MouthBreaks down

starches into simpler sugars

Pepsin Stomach Breaks down proteins

Maltase, lactase, sucrose

Small intestine

Breaks down sugars into simpler molecules

PeptidaseBreaks down

proteins into amino acids

Trypsin and chymotrypsin

Small intestine, pancreas

Continue proteins breakdown

Amylase Continue starches breakdown

Lipase Breaks down fats

D. THE SMALL INTESTINE

Bolus

Chyme

Chyle

SEGMENTATION

D. THE SMALL INTESTINE

The final products are – amino acids, monosaccharides, fatty acids and

glycerol

E. THE LARGE INTESTINE

The site where undigested materials are transported and water absorption

happens.

F. RECTUM

The site of feces formation and temporary storage of undigested food.

G. ANUS

The site where feces are expelled out of the body.

SOME COMMON DIGESTIVE DISORDERS

1. Dental caries – tooth decay or cavity. Characterized by demineralization and destruction of the different tooth layers (enamel, dentin, cementum).

SOME COMMON DIGESTIVE DISORDERS

2. Heartburn – characterized by burning sensation in chest. It is caused by the reflux of acid from the stomach back to esophagus.

SOME COMMON DIGESTIVE DISORDERS

3. Gastric ulcer (stomach ulcer) – caused by H. pylori. The caustic effects of acid and pepsin reach the walls of the stomach and cause lesions.

SOME COMMON DIGESTIVE DISORDERS

4. Appendicitis – inflammation of appendicitis. The result of obstruction of the inside space of appendix. The appendix then accumulates mucus and swells.

SOME COMMON DIGESTIVE DISORDERS

5. Diarrhea – characterized by having three or more loose liquid bowel movements per day.